All day Monday New York City was blanketed with a gas-like odor. Officials said it wasn’t harmful and there was no terrorism involved, though a few buildings were evacuated, PATH trains into the city were shut down for a while, and about a dozen people were hospitalized with breathing problems. Officials originally suspected the odor was caused by mercaptan, the chemical added to natural gas to give it a detectable smell, but today they changed their minds. Now they say it drifted across the Hudson River from the Garden State. New Jersey officials are pooh-poohing the idea, so to speak, asserting that “He who smelt it, dealt it.”